I. Field of the Invention
The present invention relates generally to devices for lubricating bearings which rotatably support a shaft within a turbine housing and, more particularly, to such a device which centrifugally injects lubricant into the bearing as it restrains the axial position of the bearing.
II. Description of the Prior Art
Lubrication of bearings which rotatably support a shaft within a turbine housing is necessary for cooling and the reduction of friction between the bearing parts. The bearings commonly comprise ball bearings in which a plurality of balls are disposed between the outer surface of a substantially annular inner race and the inner surface of a substantially annular outer race. A bearing retainer circumferentially spaces the bearings around the races and retains the balls in position. It is the abutting surfaces of the ball and the races that must be lubricated to avoid the friction which causes heat build up and resistance to rotation.
One previously known apparatus for lubricating ball bearings comprises the use of injectors which direct a stream of lubricant toward the movable bearing parts. These injectors often comprise nozzles or tubes which direct the flow of pressurized lubricant toward the bearing. Thus, it is necessary to provide a pump or other pressurized source in order to activate the lubricant injectors. Consequently, such apparatus are quite expensive and involve a large number of components which significantly increase the weight of the turbine engine. Since the injectors are stationary and spaced from rotating elements secured to the shaft, it is difficult to accurately align the injector with respect to the bearing. Consequently, not all of the lubricant passing through the injector enters the bearing. Moreover, such devices are quite inefficient since much of the spray directed from the nozzle diverges and is wasted by being reflected from adjacent surfaces.
Another known form of device for lubricating a ball bearing and supporting a rotating shaft in a turbine housing is disclosed in U.S. Pat. No. 3,264,043 to Keen. Keen avoids the need for pumps or otherwise prime or pressurized sources by relying upon gravity and centrifugal force to lubricate the ball bearing. Keen discloses a turbine having a vertically mounted shaft in which the upper portion of the ball bearing is lubricated by fluid which is pulled downwardly through appropriate passages by gravity. The lower portion of the bearing is lubricated by an elaborate passage means defined between an annular member secured to the turbine housing and a bearing retaining member secured to the shaft adjacent the inner race of a bearing. The retaining members includes an outwardly inclined exterior surface extending upwardly toward the ball in the bearing. The radially adjacent annular member includes a helical groove likewise inclined upwardly toward the ball and is secured to an extended portion of the turbine housing. The passageway defined between the surface of the retaining member and the helical groove is fluidly connected to an adjacent passage defined by a portion of the turbine housing and a beveled surface of the inner race of the bearing. That passage is in turn coupled to an annular groove in the bearing retaining member which in turn distributes the lubricant to fluid passages in the retaining member.
Such a construction is disadvantageous in that the slant of the helical groove cooperates with the angular momentum of the centrifugally forced lubricant only when the shaft is rotated in a single direction. Moreover, the large number of passages and corresponding surfaces which contact the lubricant before it reaches the bearing reduces the cooling effect of the lubricant supplied to the bearing. In addition, since the flow imparted by the centrifugal force is not driven axially into the bearing but is redirected through a passageway angled toward the bearing, this lubricating assembly can create energy losses in the flow of lubricant and can contribute to reflection of the lubricant from the bearing surfaces.